The world champion had already hinted that he was unhappy that Yamaha was trying to balance two number one riders, and although rumours of a 2010 team switch have been dismissed, Rossi has now confirmed that he has a Ducati offer on the table and that he will accept if Yamaha chooses Lorenzo over him.
When asked by BBC Sport if he still wanted to finish his career with Yamaha, Rossi replied: "I'm not 100 per cent sure, it depends what happens next year. It depends on my performance, and the decision of Yamaha for 2011. I think Yamaha has to decide between me and Jorge for 2011."
Rossi admitted that he was tempted by the prospect of riding for an Italian team, but insisted he would prefer to remain with Yamaha - and that he had made no firm decisions yet.
"It's early to say, and I have a great option with Ducati - to change bikes and try to win with an Italian bike," he said.
"For sure it's a great motivation, but at this moment I'd prefer to stay with Yamaha because I think the relationship between me and Yamaha is something special, and to change bike would be like something unfaithful.
"So I think for Yamaha I think it's very important that I finish my career with Yamaha, and also it's important for me."
Despite not wanting to Lorenzo to remain his team-mate, Rossi said he enjoyed racing with the Spaniard, having fought with him for the title this year.
"I like Jorge's approach to racing, because he likes the battle," said the seven times MotoGP champion. "He tries to the maximum, he battles, he's aggressive, but not too much, and that's so important."
Rossi joined Yamaha from Honda in 2004, and stunned the motorcycling world by taking the hitherto struggling company to the world championship at the first attempt. He has since won a further three titles.
Although Rossi was a clear number one when paired with Carlos Checa in 2004 and Colin Edwards from 2005 to 2007, the arrival of double 250cc champion Lorenzo last year provided a much stronger challenge, with Yamaha indicating that it regarded the Spaniard as its future title hope once Rossi retires.
Lorenzo's rookie season was hampered by a series of massive crashes, but this year he was able to push Rossi for the title until the penultimate round.